Adolescent idiopathic scoliosis, bracing, and the Hueter-Volkmann principle.

BACKGROUND CONTEXT Evidence demonstrating the biomechanical effects of the Hueter-Volkmann principle on vertebral body growth in spinal deformities is lacking. Bracing a scoliotic curve should, in theory, unload the growth plates on the concave side of the vertebral bodies near the curve's apex. Growth stimulation, leading to structural remodeling of the vertebral bodies, on the curve's concave side may explain the improvement or lack of curve progression, as measured by Cobb angles, reported with successful brace management of adolescent idiopathic scoliosis (AIS). PURPOSE To determine whether brace treatment stimulated asymmetric chondrogenesis in the apical three vertebral bodies. STUDY DESIGN A prospective cohort of patients with AIS receiving brace treatment were followed from the initiation of brace treatment until skeletal maturity. Patients were then retrospectively divided into those with and without radiographic progression. This post hoc analysis was included to determine risk factors for curve progression. PATIENT SAMPLE Forty-one skeletally immature patients with AIS meeting criteria for brace treatment were followed until skeletal maturity. All patients were treated with thoracolumbosacral orthotics (TLSOs). OUTCOME MEASURES The positional derotation of the TLSO on the spine was measured by comparing the initial radiograph with the first radiograph in a brace. The long-term structural changes of the vertebral bodies were determined by comparing the initial and final radiographs. Differences in initial radiographic parameters between the groups of patients with AIS with and without curve progression indicated predictive factors for successful brace treatment. METHODS Initial radiographic measurements were compared with those observed in a brace and those observed at final follow-up. The same analysis was retrospectively repeated comparing patients with AIS with and without radiographic progression. RESULTS Cobb measurements (p=.0001) and concave-to-convex height ratios of the apical three vertebral bodies improved when the brace was initially applied (p=.0035). Structural remodeling or a rotational correction of the apical three vertebral bodies was appreciated only in patients with flexible curves (p=.01). CONCLUSION Brace application results in immediate positional derotations of the spine in patients with AIS. These positional derotations were maintained only in patients with flexible curves, at final follow-up. Brace treatment was not recommended in patients whose curves did not correct at least 20% in a TLSO.